Wi-Fi is a technology for wireless local area networking based on the Institute of Electrical and Electronics Engineers (IEEE) 802.11 standards. Devices that can use Wi-Fi technology include personal computers, video-game consoles, smartphones, digital cameras, tablet computers, digital audio players, and modern printers. Wi-Fi compatible devices can connect to the Internet via a Wireless Local Area Network (WLAN) network and a wireless Access Point (AP).
Wi-Fi devices typically operate using two unlicensed bands: the 2.4 Gigahertz (GHz) band and the 5 GHz band. The 5 GHz band is shared by other non-Wi-Fi devices, such as weather radars. In many countries, Wi-Fi systems operating in the 5 GHz band are required to employ a radar detection and avoidance capability. One such avoidance capability is known as Dynamic Frequency Selection (DFS). As per the 802.11 specifications, if an AP wishes to operate or re-enter a DFS channel (i.e., a frequency channel in the 5 GHz band that may be used by other systems, such as radar), the AP is required to monitor the DFS channel of interest for a specified time period (e.g., n minutes) before it can use the channel for data transmission. The value of n may typically be between one and 10 minutes. When a radar pulse is detected, the AP must exit the channel. The monitoring and subsequent re-entry of the DFS channel may be repeated every time a radar pulse is detected.
Use of the DFS channels for Wi-Fi communications is desirable, as these channels may tend to be less crowded and provide relatively high performance. However, the requirement of monitoring the DFS channels for a specific duration can be expensive in terms of radio resources and time. Additionally, certain locations, such as those in proximity to weather stations or airports, may not be practically useable with DFS channels, as the high periodicity of the occurrence of DFS events in these locations may result in a poor Wi-Fi experience.